The present invention generally relates to monitoring dynamic motion of a vehicle and, more particularly, relates to an apparatus and method for measuring vehicle velocities using a plurality of on-board global positioning system (GPS) receiving antennas.
Automotive vehicles are commonly equipped with multiple sensing devices for sensing dynamic movement of the vehicle and generating output signals indicative of the sensed movement. The sensed vehicle dynamics output signals are typically made available to various on-board vehicle control systems to further enhance the vehicle driving performance. Advanced vehicle dynamics control systems, including active suspension control, traction control, and brake control systems, often employ sensed vehicle dynamics information such as roll angle, pitch angle, yaw rate, roll rate, pitch rate, lateral and longitudinal velocity, lateral and longitudinal acceleration, tire slip, tire slip rate, and other sensed vehicle parameters. Given a variety of sensed vehicle dynamics measurements, the vehicle dynamic control systems are able to adaptively adjust the vehicle ride, such as providing enhanced vehicle tilt control.
The above-mentioned and other vehicle dynamics parameters are generally sensed using various conventional sensors, some of which are costly and complex, and others of which suffer from noise and bias errors. Many commercially available angular yaw rate, roll rate, and pitch rate sensors exhibit inherent voltage drift/bias problems and, thus, require the additional use of drift compensation circuitry to compensate for the presence of drift error. The requirement of drift compensation circuitry further adds to the cost and complexity of the sensor. The use of a large number of such sensors can significantly add to the overall cost of the vehicle.
Accordingly, it is therefore desirable to provide for a vehicle dynamics sensing approach for sensing certain vehicle dynamics parameters in a manner that achieves cost affordable sensing. In particular, it is desirable to provide for a vehicle dynamics sensing approach that senses angular rate of change of the vehicle, such as roll rate, pitch rate, and yaw rate, and does not require the use of expensive drift compensation circuitry. It is also desirable to provide for a cost affordable vehicle dynamic sensing approach that senses inertial velocity and acceleration of the vehicle. It is further desirable to provide for a sensing approach that may complement existing sensors within the vehicle to provide for enhanced vehicle dynamics sensing at a low cost.
The present invention provides for an apparatus and method for measuring dynamic movement of a vehicle by employing multiple GPS signals and determining velocity based on a change in the carrier frequency due to Doppler effect to achieve a cost-effective vehicle dynamics measurement. According to one aspect of the present invention, the apparatus includes a first receiving antenna installed on a vehicle at a first known location for receiving GPS signals broadcast from multiple GPS transmitters, and a second receiving antenna installed on the vehicle at a second known location for receiving the GPS signals. The second receiving antenna is arranged on the vehicle at a predetermined distance from the first receiving antenna. The apparatus further has a controller for processing the GPS signals received by the first and second receiving antennas and monitoring a carrier frequency associated with each of the received GPS signals. A change in the carrier frequency of the GPS signals based on Doppler effect is determined. The controller further determines a first inertial velocity vector (i.e., velocity vector in an inertial coordinate) for the first antenna and a second inertial velocity vector for the second antenna based on the changes in the carrier frequency, and further determines an angular rate of the vehicle based on the first and second inertial velocity vectors.
According to another aspect of the present invention, an apparatus and method for measuring vehicle inertial velocity using GPS signals is provided. The apparatus includes a first receiving antenna installed on a vehicle at a first known location for receiving GPS signals broadcast from multiple GPS transmitters, and a second receiving antenna installed on the vehicle at a second known location for receiving the GPS signals. The second receiving antenna is arranged on the vehicle at a predetermined distance from the first receiving antenna. The apparatus further includes a controller for processing the received GPS signals received from the first and second receiving antennas and monitoring a carrier frequency associated with the received GPS signals. The controller determines a change in the carrier frequency of the GPS signals due to Doppler effect. The controller further determines a first inertial velocity vector for the first antenna, and a second inertial velocity vector for the second antenna, based on the change in carrier frequency. The controller obtains a vehicle heading and determines at least one of longitudinal and lateral velocity vectors of the vehicle as a function of the first and second inertial velocity vectors and the vehicle heading.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.